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PubMed2003

Komrower Lecture. Congenital disorders of glycosylation (CDG): it's all in it!

Congenital disorders of glycosylation (CDGs) are due to defects in the synthesis of the glycan moiety of glycoproteins or other glycoconjugates. This review is devoted mainly to the clinical aspects of protein glycosylation defects. There are two main types of protein glycosylation: N-glycosylation and O-glycosylation. N-glycosylation generally consists of an assembly pathway (in cytosol and endoplasmic reticulum) and a processing pathway (in endoplasmic reticulum and Golgi). O-glycosylation lacks a processing pathway but is otherwise more complex. Sixteen disease-causing defects are known in protein glycosylation: 12 in N-glycosylation and four in O-glycosylation. The N-glycosylation defects comprise eight assembly defects (CDG-I) designated CDG-Ia to CDG-Ih, and four processing defects (CDG-II) designated CDG-IIa to CDG-IId. By far the most frequent is CDG-Ia (phosphomannomutase-2 deficiency). It affects the nervous system and many other organs. Its clinical expression varies from extremely severe to very mild (and thus probably underdiagnosed). The most interesting disease in this group is CDG-Ib (phosphomannose isomerase deficiency) because it is so far the only efficiently treatable CDG (mannose treatment). It has a hepatic-intestinal presentation. The O-glycosylation defects comprise two O-xylosylglycan defects (a progeroid variant of Ehlers-Danlos syndrome and the multiple exostoses syndrome) and two O-mannosylglycan defects (Walker-Warburg syndrome and muscle-eye-brain disease). All known CDGs have a recessive inheritance except for multiple exostoses syndrome, which is dominantly inherited. There is a rapidly growing group of putative CDGs with a large spectrum of clinical presentations (CDG-x). Serum transferrin iso-electrofocusing remains the cornerstone of the screening for N-glycosylation defects associated with sialic acid deficiency. Abnormal patterns can be grouped in to type 1 and type 2. However, a normal pattern does not exclude these defects. Screening for the other CDGs is much more difficult, particularly when the defect is organ- or system-restricted. The latter group promises to become an important new chapter in CDG. It is concluded that CDGs will eventually cover the whole clinical spectrum of paediatric and adult disease manifestations.

Bacterial Proteins↗
PubMed1998

Tout-velu is a Drosophila homologue of the putative tumour suppressor EXT-1 and is needed for Hh diffusion.

Hedgehog (Hh) proteins act through both short-range and long-range signalling to pattern tissues during invertebrate and vertebrate development. The mechanisms allowing Hedgehog to diffuse over a long distance and to exert its long-range effects are not understood. Here we identify a new Drosophila gene, named tout-velu, that is required for diffusion of Hedgehog. Characterization of tout-velu shows that it encodes an integral membrane protein that belongs to the EXT gene family. Members of this family are involved in the human multiple exostoses syndrome, which affects bone morphogenesis. Our results, together with the previous characterization of the role of Indian Hedgehog in bone morphogenesis, lead us to propose that the multiple exostoses syndrome is associated with abnormal diffusion of Hedgehog proteins. These results show the existence of a new conserved mechanism required for diffusion of Hedgehog.

Amino Acid Sequence↗
PubMed2001

[Rare case of popliteal artery injury caused by distal femoral exostosis. Case report].

Complications of multiple exostoses occur rarely and articles about it can be found occasionally. We found reasonable to report our case because of its rarity. A female patient of 17 was under treatment in the Orthopaedic Clinic with multiple exostoses. Before her admission to the Clinic, a suddenly, painful swelling in the distal-third of the left femur occurred, and then a well detailed examination has done (bone radiograph, angiogramm, MR). The examinations arised the presence of pseudoaneurysm as a background of the swelling of the soft tissue, as well as the possibility of juvenile bone tumor at the same time. During the operation we detected a sharp exostosis on the distal medial condyle of the femur, which occurred a lesion on the popliteal artery. It was the base of forming the pseudoaneurysm. As a conclusion we would like to underline that during the attend of such cases, the presence of vascular surgical team is necessary.

Adolescent↗
PubMed1999

Langer-Giedion syndrome associated with submucous cleft palate.

We report a 4-year-old girl with characteristic features of the Langer-Giedion syndrome (trichorhinophalangeal syndrome type II) who also had submucous cleft palate. When she underwent a palatoplasty, a diagnosis of Langer-Giedion syndrome was made because of the characteristic facial features, multiple exostoses, and partial deletion of the long arm of chromosome 8. This is the first case of trichorhinophalangeal syndrome associated with cleft palate. We review the clinical alterations of trichorhinophalangeal syndromes and differential diagnosis of Langer-Giedion syndrome from trichorhinophalangeal syndrome type I and hereditary multiple exostoses. We also describe the importance of trichorhinophalangeal syndrome in plastic surgery.

Cephalometry↗
PubMed1986

Scintigraphic findings of multiple osteochondromas.

Multiple osteochondromas (hereditary multiple exostoses, diaphyseal aclasis, cartilagenous exostoses) are anomalies of bone development in which multiple cartilagenous exostoses grow out from the cortical surface, mainly involving ends of the long bones. While radiographic characteristics of multiple osteochondromas have been well documented, there is little information concerning the place of bone imaging in this disease. A patient with multiple osteochondromas whose skeletal scintigrams correlate with the concurrent radiographs is presented. Although there is no specific pattern scintigraphically, the abnormal, irregular increase in radioactivity at the end of the long bones may raise a possibility of this disease entity.

Adult↗
PubMed1985

[Trichorhinophalangeal syndrome. Apropos of a case].

The trichorhinopharyngeal (TRP) syndrome type I (Giedion, 1966) is characterized clinically by craniofacial dysmorphism with sparse hair, pear-shaped nose and long philtrum, and abnormalities of the extremities (disabling deformities of the hands and feet). The diagnosis is confirmed by the finding, at radiology, of cone-shaped epiphyses at the base of the middle phalanges. The discovery of patients presenting with other clinical and radiological abnormalities (growth retardation, microcephaly, mental retardation, multiple exostoses) has led to the individualization of a type II syndrome (Langer-Giedion, 1969). We report here a new case of TRP type I and review current data concerning the syndrome, notably the clinical and genetic differences between types I and II. Our case concerned a 43-year-old female patient who consulted for sparse, fine, brittle and very unaesthetic hair obliging her to wear a wig permanently. Examination disclosed other morphological abnormalities, including disabling deformities of the extremities (clinobrachydactyly of the hands and feet which had been present since the age of 6-7 years) and peculiar facial features with a globulous, pear-shaped nose and a long philtrum. She was of small size and had no mental retardation. These clinical symptoms and the finding of cone-shaped epiphyses (type 12) at the base of the middle phalanges led to affirm diagnosis of TRP type I. The case appeared to be solitary. The TRP syndrome was individualized by Giedion in 1966. It is usually detected during the later childhood. In 1969, Langer and Gorlin reported similar features in patients who, in addition, presented with multiple exostoses (hands and feet and body skeleton).(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Multiple↗
PubMed2002

Transgenic expression of the EXT2 gene in developing chondrocytes enhances the synthesis of heparan sulfate and bone formation in mice.

Hereditary multiple exostoses (HME), a dominantly inherited disorder characterized by multiple cartilaginous tumors, is caused by mutations in the gene for, EXT1 or EXT2. Recent studies have revealed that EXT1 and EXT2 are required for the biosynthesis of heparan sulfate and exert maximal transferase activity as a complex. The Drosophila homologue of EXT1 (tout-velu) regulates the movement and signaling of Hedgehog protein, which plays an important role in the regulation of chondrocyte differentiation and bone development. In this study, to investigate the biological role of EXT2 in bone development in vivo and the pathological role of HME mutations in the development of exostoses, we generated transgenic mice expressing EXT2 or mutant EXT2 in developing chondrocytes. Histological analyses and micro-CT scanning showed that the biosynthesis of heparan sulfate and the formation of trabeculae were upregulated in EXT2-transgenic mice, but not in mutant EXT2-transgenic mice. The expression of EXT1 is concomitantly upregulated in EXT2-transgenic and even mutant EXT2-transgenic mice, suggesting an interactive regulation of EXT1 and EXT2 expression. These findings support that the EXT2 gene encodes an essential component of the glycosyltransferase complex required for the biosynthesis of heparan sulfate, which may eventually modulate the signaling involved in bone formation.

Animals↗
PubMed1984

Correlative radiographic, scintigraphic, and histological evaluation of exostoses.

We reviewed the cases of twenty-four patients with solitary or multiple exostoses to correlate their radiographic, scintigraphic, and histological evaluations. We studied twenty-five excised lesions, two of them exostotic chondrosarcomas, from twenty-two patients. There were two patterns of bone-scan activity and there was a direct correlation between enchondral bone formation and radionuclide uptake in all patients, both skeletally immature and mature. So-called quiescent lesions--those with inactive scans--were those that lacked histological evidence of enchondral bone formation. Those with increased uptake--active exostoses--all demonstrated active formation of enchondral bone. Evidence of active exostotic growth could be demonstrated on bone scans well beyond the time of skeletal maturity. The bone scan did not qualitatively differentiate the benign active exostoses from the two lesions with malignant degeneration. Increased uptake related to enchondral bone formation was a feature of both. An inactive scan, however, seemed to exclude the possibility of malignant degeneration in the exostosis.

Adult↗
PubMed1987

Cytogenetics of Mendelian mutations associated with cancer proneness.

About 5% of Mendelian mutations displaying neoplastic tendencies are associated with chromosomal aberrations. The best established examples are retinoblastoma and del(13)(q14) and aniridia-Wilms' tumor and del(11)(p13). Evidence suggests that both mutations behave as dominant traits in the individual and as recessive traits in the cells. DNA analysis indicates that tumorigenesis arises from homozygosisty for the mutant allele at these loci, as a consequence of mitotic nondisjunction or from a mitotic recombination event. An additional argument for this conclusion is provided by the demonstration of duplication of 11p15 in some patients with the Beckwith-Wiedemann syndrome, which is complicated often by Wilms' tumor and other embryonal tumors. Data obtained with molecular probes have shown that also rhabdomyosarcoma and hepatoblastoma arise by homozygosity for a mutant allele at a locus on 11p, suggesting ontogenic relatedness of these tumor types. Additional examples of Mendelian mutations associated with chromosome deletions and neoplasia include Langer-Giedion syndrome with multiple exostoses and del(8)(q24.1), multiple endocrine neoplasia and del(20)(p12.2). While the presence of specific chromosome changes in subjects with high susceptibility to neoplasia does pinpoint the location of DNA sequences involved in the predisposition to certain types of cancers, selected Mendelian mutations associated with chromosome instability and cancer proneness may elucidate biological principles of cell proliferation and transformation. However, our current knowledge of mechanisms resulting in increased frequency of chromosome breakage and cancer susceptibility in ataxia-teleangiectasia, Fanconi's anemia, Bloom's syndrome, and similar conditions are still very incomplete.

Chromosome Aberrations↗
PubMed2000

Correction of ankle valgus deformity secondary to multiple hereditary osteochondral exostoses with Ilizarov.

The following case report highlights basic aspects of Multiple Hereditary Osteochondral Exostoses (MHOCE) and discusses the successful treatment of an adult with ankle pain secondary to growth arrest and foreshortening of the fibula. Two salient features include the age of the patient at presentation and the success of the procedure. Symptomatic valgus deformities of the ankle secondary to MHOCE are normally corrected during adolescence, prior to physeal closure. Reducing the ankle mortise by distally displacing the fibula and correcting rotational and angular ankle deformities with Ilizarov external fixation improved this patient's ankle function and relieved his pain.

Adult↗